β-Nickel hydroxide cathode material for nano-suspension redox flow batteries
Yue LI , Cheng HE , Elena V. TIMOFEEVA , Yujia DING , Javier PARRONDO , Carlo SEGRE , Vijay RAMANI
Front. Energy ›› 2017, Vol. 11 ›› Issue (3) : 401 -409.
β-Nickel hydroxide cathode material for nano-suspension redox flow batteries
As part of an effort to build a prototype flow battery system using a nano-suspension containing β-Ni(OH)2 nanoparticles as the cathode material, nano-sized β-Ni(OH)2 particles with well-controlled particle size and morphology were synthesized via the one-step precipitation of a NiCl2 precursor. The composition and morphology of the nanoparticles were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The XRD patterns confirmed that β-Ni(OH)2 was successfully synthesized, while SEM results showed that the particle sizes range from 70 to 150 nm. To ensure that Ni(OH)2 could be employed in the nano-suspension flow battery, the electrochemical performance of the synthesized β-Ni(OH)2 was initially tested in pouch cells through charge/discharge cycling. The phase transformations occurring during charge/discharge were investigated usingin-situ X-ray absorption spectroscopy to obtain the shift in the oxidation state of Ni (X-ray adsorption near edge structure, XANES) and the distances between Ni and surrounding atoms in charged and discharged states (extended X-ray absorption fine structure, EXAFS). XANES results indicated that the electrode in the discharged state was a mixture of phases because the edge position did not shift back completely. XAFS results further proved that the discharge capacity was provided by β-NiOOH and the ratio between β-Ni(OH)2 and g-NiOOH in the electrode in the discharged state was 71:29. Preliminary nano-suspension tests in a lab-scale cell were conducted to understand the behavior of the nano-suspension during charge/discharge cycling and to optimize the operating conditions.
nano-suspension flow battery / β-Ni(OH)2 / scanning electronic microscopy (SEM) / X-ray diffraction (XRD) / X-ray adsorption near edge structure (XANES) / extended X-ray absorption fine structure (EXAFS)
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Higher Education Press and Springer-Verlag Berlin Heidelberg
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